About 1.9 million, or 55 percent, of New York workers commuted by subway or bus in 2005, according to the U.S. Census Bureau's latest American Community Survey. Chicago had about 294,000 public transportation commuters, or 25 percent of its 1.2 million workers.

The report covered the 50 cities with the most workers aged 16 or above.

Five of the top 10 public cities, by percentage, were on the Washington to Boston corridor with Baltimore and Philadelphia residents the other frequent users.

Washington had the second highest ratio of public transit users at 37.7 percent. In no other city did the percentage rise above a third. In Los Angeles, the nation's second biggest city, only 171,639 workers, or 10.3 percent, commuted by bus or rail.

Southwestern, Southern and Mountain cities had among the lowest ratios of mass transit commuters. Only 0.4 percent of Arlington, Texas residents and 0.5 percent of Wichita, Kansas and Virginia City, Virginia, used public transportation.

In this era of high gas prices and heightened "green" awareness, moving commuters off the road and into public transportation can cut auto emissions, energy use and, it is hoped, global warming.

And, if Mayor Mike Bloomberg gets his way, even more New Yorkers may soon be boarding trains to get to work.

Bloomberg has proposed a congestion-pricing plan that will charge motorists to travel into the business district of Manhattan during peak hours. The idea is to discourage them from driving to work.

Any money raised is supposed to be applied to the subways and buses, which would help keep transit fares low - currently they are $2 for a subway ride but less with volume discounts and monthly or weekly plans.

Some cities do encourage car-pooling to reduce congestion and lessen energy use. As a result, about one tenth of all U.S. workers car pool, more than three quarters of them with just a single other occupant, according to the census study.

The study also said Mesa, Arizona (16.7 percent), Phoenix (16.2 percent) and Sacramento (15.7 percent) have the highest ratios of car-pooling commuters.

In Portland, Oregon one of the major commuting methods of choice is two-wheelers. The study said more Portlanders bike to work than anywhere else - 3.5 percent of the workforce. That's about eight times higher than the national average of 0.4 percent.

Boston is the leading walk-to-work city; 13.5 percent of its residents commute by riding shank's mare, well above the 2.5 percent national average.